This Application is a Section 371 National Stage Application of International Application No. PCT/FR00/03658 filed Dec. 21, 2000 and published as WO 01/46354 on Jun. 28, 2001, not in English.
1. Field of the Invention
The invention concerns the field of extraction chemistry.
2. Background of the Invention
More precisely, the present invention relates to the extraction of fatty material from natural raw materials.
The fatty materials, principally those of plant origin, are ingredients widely used by the food, cosmetic and pharmaceutical industries.
However, these fatty materials may rarely be used in the crude state and must generally be subjected to a refining in order to remove one or more undesirable components, the nature of which depends on the applications provided for the refined product.
Thus, the cosmetic and pharmaceutical industries use fatty materials enriched in unsaponifiable materials that is according to the French standard NFT 60-205-1 in substances which, after saponification of the fatty material by potassium hydroxide and extraction by a specified solvent, are not volatile under specified conditions. The fatty materials enriched in unsaponifiables have particularly high contents of hydrocarbons, heavy alcohols (aliphatic or terpene), sterols and tocopherols and are obtained after removal of a part of the triglycerides which are the predominant components of the crude fatty material.
Among the numerous extraction and fractionation methods of fatty materials proposed in the state of the technique, solvent extraction is a very widespread technique which is available according to numerous technological variants.
Thus, the patent application FR 2 702 773 proposes a method for preparation of fractions of plant fatty materials enriched in unsaponifiable materials. In this method, the plant fatty material is treated with acetone so as to recover, on the one hand a fraction insoluble with heat, rich in unsaponifiable and on the other hand, a soluble fraction subjected later to a cold crystallization step. After filtration of the precipitate, the filtrate is evaporated to dryness. The evaporation residue also forms a fraction enriched in unsaponifiable. On the other hand, the precipitate is enriched in triglycerides.
It will be noted that, according to the raw material from which they are extracted, the plant fatty materials have different compositions, qualitatively and quantitatively. These differences may justify the use of solvents different from acetone (for example, hexane or ethanol) as much at the hot extraction step as at the cold precipitation step.
The principal drawback of the extraction and fractionation methods by solvent results from the use of organic solvents (alkanes, ketones, esters, alcohols, ethers, chlorinated solvents) which subject the extract obtained to regulatory constraints related to the contents of residual solvents. In fact, whatever their nature, these organic solvents are either harmful or toxic. This harmfulness and this toxicity are demonstrated at generally low contents of residual solvents in the extracts obtained. In order to eliminate the health-related risks, therefore it is necessary to use desolvation methods which present several drawbacks. In fact, beside the additional cost that they incur, these desolvation methods, according to the operating conditions applied, may have a negative effect on the quality of the extracts thus treated.
These constraints also concern the risks of solvent discharge in liquid or gaseous form in the natural medium. Finally, with the exception of the alkanes, the traditional extraction solvents present the drawback of not having total chemical inertness, risking leading to denaturation of the products obtained, according to the extraction conditions or storage of the extracts.
The principal objective of the present invention is to propose an extraction and fractionation method of fatty material by a solvent that does not present such drawbacks.
Such a method according to the invention is characterized in that it consists of at least one step using an extraction solvent formed by at least a hydrofluoroether (abbreviated HFE) with general formula (I):
CnF2n+1OCmH2m+1
in which n is between 3 and 6 and m is between 1 and 5 and at least one separation step leading to obtaining on the one hand a crude extract of fatty material rich in unsaponifiable materials and, possibly, in free fatty acids and on the other hand, to an extraction insoluble fraction.
These hydrofluoroethers, by comparison with conventional solvents, present the following advantages by comparison with conventional solvents.
They are non-flammable and because of this, do not require the use of specific production and protection equipment. This characteristic is very particularly interesting from the angle of production on industrial scale since it has a direct effect on the cost of the finished products;
They do not present a risk for the ecosystem and are in conformity with the strictest environmental regulations (zero potential for destruction of the ozone layer and very low contribution to the greenhouse effect);
They are chemically inert, odorless, colorless and flavorless. Therefore, they do not have any negative effect on the properties of extracts or formulations which contain them or which they are used to prepare.
Even at high doses, they are nontoxic by inhalation, absorption or repeated contact;
Finally, they have a low thermal capacity and latent heat of vaporization compared with those of organic solvents currently used in extraction; therefore, the method according to the invention is not very costly in energy.
Preferentially, said hydrofluoroether is chosen from methoxynonafluorobutane with formula C4F9xe2x80x94Oxe2x80x94CH3 (also designated in the chemical industry by the name HFE7100) and ethoxynonafluorobutane C4F9xe2x80x94Oxe2x80x94C2H5 (also designated in the chemical industry by the name HFE-7200).
These compounds present the advantage of having boiling points of 60xc2x0 C., for methoxynonafluorobutane and 78xc2x0 C. for ethoxynonafluorobutane which allow their use in traditional solid-liquid or liquid-liquid extraction equipment without notable modification of these latter. Moreover, these hydrofluoroethers may be used in the extraction methods resorting to new technologies such as microwaves or ultrasound.
It will be noted that the use of hydrofluoroethers as extraction agents has already been described in the patent PCT FR98/02546. This document discloses the solubilizing nature of the HFE for the preparation of plant extracts, however in contrast to the present invention, without bringing out the particularly selective nature of these HFE with respect to the particular classes of chemical compounds that are lipid fractions rich in unsaponifiable materials.
On the other hand, the present invention shows that the HFE, with good selectivity are likely to extract such lipid fractions rich in unsaponifiable materials.
It will be noted that this selectivity is not total since the HFE with formula (I) coextract the lipid substances not belonging to the category of unsaponifiable materials, in particular triglycerides and free fatty acids. The coextraction of free fatty acids in certain cases forms an additional advantage of the method, particularly in the case of matrixes containing free fatty acids of pharmaceutical, cosmetic or nutritional interest.
According to a preferential variant of the invention, it is possible to enrich again the crude extract of obtained fatty material, rich in unsaponifiable substances and free fatty acids, by a precipitation step selective for coextracted triglycerides consisting of cooling said crude extract to a temperature lower than the extraction temperature.
Therefore, the method according to the invention makes it possible to fractionate the fatty material into fractions enriched in unsaponifiable materials and into free fatty acids and into fractions enriched in triglycerides.
The fractions obtained may be as well suited for cosmetic applications as for pharmaceutical or food applications.
According to a preferential variant of the invention, the method comprises an additional step consisting of decanting said filtrate then evaporating the latter so as to recover a soluble extract very enriched in unsaponifiable substances and in free fatty acids.
According to another advantageous aspect of the method according to the invention, said insoluble fraction is recycled to the beginning of the method.
It will be noted that the method according to the invention could be used in the presence of at least one cosolvent chosen from alkanes, ketones, alcohols, alkyl ethers, carboxylic acids, esters, amides, halogenated hydrocarbons, acetals.
The invention as well as the different advantages that it presents will now be more easily understood as a result of the description that follows with examples that are nonlimiting for its achievement.